122 lines
3.6 KiB
Diff
122 lines
3.6 KiB
Diff
Bug 1050342. Fix a case where the fast huffman decoder in libjpeg-turbo can produce different results depending on how data is fed to it.
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This change comes from the blink repo https://codereview.appspot.com/229430043/ and is unlikely to be accepted upstream into libjpeg-turbo.
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diff --git jdhuff.c jdhuff.c
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--- jdhuff.c
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+++ jdhuff.c
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@@ -664,17 +664,17 @@ decode_mcu_fast (j_decompress_ptr cinfo,
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ASSIGN_STATE(state, entropy->saved);
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for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
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JBLOCKROW block = MCU_data ? MCU_data[blkn] : NULL;
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d_derived_tbl *dctbl = entropy->dc_cur_tbls[blkn];
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d_derived_tbl *actbl = entropy->ac_cur_tbls[blkn];
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register int s, k, r, l;
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- HUFF_DECODE_FAST(s, l, dctbl);
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+ HUFF_DECODE_FAST(s, l, dctbl, slow_decode_mcu);
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if (s) {
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FILL_BIT_BUFFER_FAST
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r = GET_BITS(s);
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s = HUFF_EXTEND(r, s);
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}
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if (entropy->dc_needed[blkn]) {
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int ci = cinfo->MCU_membership[blkn];
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@@ -682,17 +682,17 @@ decode_mcu_fast (j_decompress_ptr cinfo,
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state.last_dc_val[ci] = s;
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if (block)
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(*block)[0] = (JCOEF) s;
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}
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if (entropy->ac_needed[blkn] && block) {
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for (k = 1; k < DCTSIZE2; k++) {
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- HUFF_DECODE_FAST(s, l, actbl);
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+ HUFF_DECODE_FAST(s, l, actbl, slow_decode_mcu);
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r = s >> 4;
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s &= 15;
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if (s) {
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k += r;
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FILL_BIT_BUFFER_FAST
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r = GET_BITS(s);
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s = HUFF_EXTEND(r, s);
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@@ -701,33 +701,34 @@ decode_mcu_fast (j_decompress_ptr cinfo,
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if (r != 15) break;
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k += 15;
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}
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}
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} else {
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for (k = 1; k < DCTSIZE2; k++) {
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- HUFF_DECODE_FAST(s, l, actbl);
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+ HUFF_DECODE_FAST(s, l, actbl, slow_decode_mcu);
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r = s >> 4;
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s &= 15;
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if (s) {
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k += r;
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FILL_BIT_BUFFER_FAST
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DROP_BITS(s);
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} else {
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if (r != 15) break;
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k += 15;
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}
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}
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}
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}
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if (cinfo->unread_marker != 0) {
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+slow_decode_mcu:
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cinfo->unread_marker = 0;
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return FALSE;
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}
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br_state.bytes_in_buffer -= (buffer - br_state.next_input_byte);
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br_state.next_input_byte = buffer;
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BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
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ASSIGN_STATE(entropy->saved, state);
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diff --git jdhuff.h jdhuff.h
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--- jdhuff.h
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+++ jdhuff.h
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@@ -203,32 +203,34 @@ EXTERN(boolean) jpeg_fill_bit_buffer
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} else { \
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slowlabel: \
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if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
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{ failaction; } \
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get_buffer = state.get_buffer; bits_left = state.bits_left; \
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} \
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}
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-#define HUFF_DECODE_FAST(s,nb,htbl) \
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+#define HUFF_DECODE_FAST(s,nb,htbl,slowlabel) \
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FILL_BIT_BUFFER_FAST; \
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s = PEEK_BITS(HUFF_LOOKAHEAD); \
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s = htbl->lookup[s]; \
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nb = s >> HUFF_LOOKAHEAD; \
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/* Pre-execute the common case of nb <= HUFF_LOOKAHEAD */ \
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DROP_BITS(nb); \
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s = s & ((1 << HUFF_LOOKAHEAD) - 1); \
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if (nb > HUFF_LOOKAHEAD) { \
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/* Equivalent of jpeg_huff_decode() */ \
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/* Don't use GET_BITS() here because we don't want to modify bits_left */ \
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s = (get_buffer >> bits_left) & ((1 << (nb)) - 1); \
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while (s > htbl->maxcode[nb]) { \
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s <<= 1; \
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s |= GET_BITS(1); \
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nb++; \
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} \
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- s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) & 0xFF ]; \
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+ if (nb > 16) \
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+ goto slowlabel; \
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+ s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) ]; \
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}
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/* Out-of-line case for Huffman code fetching */
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EXTERN(int) jpeg_huff_decode
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(bitread_working_state *state, register bit_buf_type get_buffer,
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register int bits_left, d_derived_tbl *htbl, int min_bits);
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